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Biomedical subjects

K D Rao

Publications and source records attributed to K D Rao.

7 recordsLinked to original sources
PubMed2006

Imaging growth dynamics of tumour spheroids using optical coherence tomography.

Optical coherence tomography (OCT) was used to monitor the dynamics of tumour spheroid formation by the hanging drop method. In contrast to microscopy, the estimates obtained using OCT for the volume of the spheroid, were consistent with the measured changes in cell number as a function of time. The OCT images also revealed heterogeneous structures in the spheroids of approximately 200 microm diameter. These corresponded to the necrotic regions identified by fluorescence of propidium iodide stained cells.

Cell Count↗
PubMed2003

Electrostatic micromachine scanning mirror for optical coherence tomography.

Compact electrostatic micromirror structures for use in the scanning arm of an optical coherence tomography (OCT) system are described. These devices consist of millimeter-scale mirrors resting upon micrometer-scale polyimide hinges that are tilted by a linear micromachine actuator, the integrated force array (IFA). The IFA is a network of deformable capacitor cells that electrostatically contract with an applied voltage. The support structures, hinges, and actuators are fabricated by photolithography from polyimide-upon-silicon wafers. These devices were inserted into the scanning arm of an experimental OCT imaging system to produce in vitro and in vivo images at frame rates of 4 to 8 Hz.

Electricity↗
PubMed1995

On-line method for enhancement of electroencephalogram signals in presence of electro-oculogram artefacts using nonlinear recursive least squares technique.

A record of the human scalp potentials (EEG) is one of the most commonly used techniques for understanding the brain functions. While recording EEG signals, other undesired signals called artefacts get superimposed on the EEG signals. Of these, electro-oculogram generated by eye movements is found to be the most significant and common. Conventional artefact minimisation schemes use linear estimation models. However, the result in sub-optimal schemes as signal processing in the human brain is highly nonlinear. In this paper therefore an on-line technique is suggested for artefact minimisation using nonlinear recursive least squares. Results confirm the efficacy of the method.

Computers↗
PubMed1983

Changes in ovarian ultrastructure and ecdysteroid titer during the aging process of female Xyleborus ferrugineus (Coleoptera: Scolytidae).

Striking ultrastructural and hormonal parameters of premature menopause and aging are reported in female Xyleborus ferrugineus fed cholesterol, rather than 7-dehydrocholesterol, as a sole dietary sterol. The titer of free ecdysteroids in such 63-day-old females remained abnormally elevated through the period of the ovarian cycle. A similar plateauing of such elevated titer also occurred in 147-day-old, irregularly cycling females fed only cholesterol as the dietary sterol. These hormonal changes in menopausing X. ferrugineus females seem especially analogous to the maintenance of an elevated concentration of 17-beta-estradiol through the estrous, as well as the proestrous, ovary of aged irregularly cycling rats. The highly abnormal ultrastructure of ovaries of X. ferrugineus females aged 216 days on a diet containing cholesterol as the sole sterol seems quite analogous to that of the nonovulatory follicles in older, irregularly cycling rats. Our new findings involving aging X. ferrugineus females indicate further the usefulness of an insect model to study aging processes.

Aging↗
PubMed1980

Ultrastructure of the prothoracic gland of variously aged female pupae of Xyleborus ferrugineus and associated ecdysteroid titers.

The prothoracic glands of female pupae of Xyleborus ferrugineus at three ages (0-h, 48-h, and 72-h-old) were examined for ultrastructural changes that correlate with high titers of ecdysteroids in the entire pupa. In all three ages, the prothoracic gland cells appear compact with a prominent nucleus. Lysosome-like structures with concentrically oriented internal membrane are observed in both 0-h and 72-h-old gland cells. Mitochondria are abundant in the glands of both ages, and rough endoplasmic reticulum is relatively sparse. Numerous microtubules are present in the prothoracic gland cells of 48-h-old female pupae that contain relatively high titers of ecdysteroids. Rough endoplasmic reticulum also is especially abundant at this age of the pupa. Ecdysone titers, estimated by the radioimmunoassay method (RIA), were 161.04 +/- 26.80 pg/mg, 704.25 +/- 69.02pg/mg and 298.72 +/- 26.80pg/mg body weight in 0-h, 48-h and 72-h-old female pupae, respectively.

Animals↗